1. Field of the Invention
The present invention relates to a wired circuit board and, more particularly, to a wired circuit board having terminals to be connected to external terminals through molten metal.
2. Description of the Prior Art
A wired circuit board usually has terminals to be connected to external terminals as a part of a conductive pattern.
Molten metal, such as, for example, solder balls, is used for connecting the terminals of the wired circuit board to the external terminals. The solder balls are placed on the terminals and are melted on the surfaces of the terminals, whereby the terminals of the wired circuit board are connected to the external terminals through the solder balls.
When the terminals have flat surfaces, the solder balls can roll around the surfaces of the terminals. Prior art proposes an attempt solution that electrodes (terminals) formed on the substrate are provided, at center portions thereof, with cavities to place the solder balls on the electrodes stably (Cf. JP Laid-open (Unexamined) Patent Publication No. 11-266066 (1999), for example).
In this prior art of JP Laid-open (Unexamined) Patent Publication No. 11-266066 (1999), the electrodes are formed as ring-shaped electrodes and the cavities are formed at the center portions of the ring-shaped electrodes, while the substrate is exposed from lower ends of the cavities, in other words, the cavities are closed by the substrate.
On the other hand, when the electrodes are connected to the external terminals through the solder balls, the substrate of the wired circuit board and an external substrate must be placed to confront each other so that the solder balls can be sandwiched therebetween. However, when the substrate and the external substrate are placed to confront each other, it cannot disadvantageously be seen whether the solder balls are precisely set in the cavities in the electrodes, because the cavities are closed by the substrate, so the solder balls get behind the substrate.